I see. I had read that it was a source map that was leaked here specifically, but my vague understanding of the term was mostly that it might be a way to trace back JavaScript lines to the TypeScript it compiled from, since I don't have much of an understanding of all of the other various steps that are part of a JavaScript build nowadays.

I think I still disagree with the parent comment premise that "they probably thought minifying was enough", since it sounds likely they were doing all of those other steps. The issue seems like insufficient auditing of the build process (especially if agents were involved, which seems likely for Anthropic) rather than not doing all of the usual JS build stuff.